import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class code3 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String s = in.next();
        char[] ss = s.toCharArray();

        //找到次数最多的字符
        int max = 0;
        char maxch = '0';
        int[] hash = new int[26];
        for (char x : ss) {
            if (max < ++hash[x - 'a']) {
                maxch = x;
                max = hash[x - 'a'];
            }
        }
        //是否可以重排
        if (max > (n + 1) / 2) {
            System.out.println("no");
        } else {
            System.out.println("yes");
            //重排新数组
            char[] ret = new char[n];
            //先排最多的字符
            int i = 0;
            while (hash[maxch-'a']-- != 0) {
                ret[i] = maxch;
                i += 2;
            }
            //排剩下的字符
            for(int j=0;j<26;j++) {
                if(hash[j] != 0 && maxch != (char)(j + 'a')) {
                    while(hash[j]-- != 0) {
                        if(i >= n) {
                            i = 1;
                        }
                        ret[i] = (char)(j + 'a');
                        i += 2;
                    }
                }
            }

            //返回结果
            for (int j = 0; j < n; j++) {
                System.out.print(ret[j]);
            }
        }

    }
}